Can Shear-Wave Elastography be Used to Discriminate Obstructive Hydronephrosis from Nonobstructive Hydronephrosis in Children?

Abstract

To determine if ultrasonographic (US) renal shear-wave speed (SWS) measurements obtained either before or after intravenous diuretic administration can be used to discriminate obstructive hydronephrosis from unobstructive hydronephrosis in children, with diuretic renal scintigraphy as the reference standard. Institutional review board approval and parental informed consent were obtained for this HIPAA-compliant prospective cross-sectional blind comparison with a reference standard. Between November 2012 and September 2014, 37 children (mean age, 4.1 years; age range, 1 month to 17 years) underwent shear-wave elastography of the kidneys immediately before and immediately after diuretic renal scintigraphy (reference standard for presence of urinary tract obstruction). Median SWS measurements (in meters per second), as well as change in median SWS (median SWS after diuretic administration minus median SWS before diuretic administration) were correlated with the amount of time required for kidney radiotracer activity to fall by 50% after intravenous administration of the diuretic (T1/2). Median SWS measurements were compared with degree of obstruction and degree of hydronephrosis with analysis of variance. Receiver operating characteristic (ROC) curves were created. Radiotracer T1/2 values after diuretic administration did not correlate with median SWS measurements obtained before (r = -0.08, P = .53) or after (r = -0.0004, P >.99) diuretic administration, nor did they correlate with intraindividual change in median SWS (r = 0.07, P = .56). There was no significant difference in pre- or postdiuretic median SWS measurements between kidneys with scintigraphic evidence of no, equivocal, or definite urinary tract obstruction (P > .5) or for median SWS measurements between kidneys with increasing degree of hydronephrosis (P > .5). ROC curves showed poor diagnostic performance of median SWS in discerning no, equivocal, or definite urinary tract obstruction (area under the ROC curve ranged from 0.50 to 0.62). US SWS measurements did not enable discrimination of obstructive hydronephrosis from unobstructive hydronephrosis in children.